1) Actino Rise - I can't even get one star on this bastard.
2) Atrium One - Two stars after spending several hours on it.
3) Shard One - Barely got two stars. I rarely pulled off the "two for one jump".
4) Playground Three - Could probably get this one with practice, but I don't need the third star on it.
I've gotten three stars on everything else I've tried. I won't bother improving on these as I only want the achievement.
1) Chapter 2 - Just too many spots to get hung up on.
2) Chapter 9 - Easy once you realize how much time you can spend taking out the guards in the server room. Only put it here due to a wierd glitch that kept happening to me at the very end.
Everything else wasn't too bad.